The present invention relates to a constant tension regulator of positively unwound flexible material, particularly of warp threads in weaving machines.
Machines are known in which it is necessary to rewind flexible material from one beam to another under constant tension. Usually, the sensing means for the constant tension value of the flexible material takes the form of a cylinder or a roller over which said material is guided. The cylinder is generally swingably mounted on a resilient swingable lever, which simultaneously exerts pressure and thereby tension upon the said flexible material. The difference between the winding speed of the flexible material on the drawing beam and its unwinding speed from the beam, which is generally due to variations in the machine operation, causes changes in tension.
This problem is encountered particularly in weaving machines. The warp threads are mounted on a warp beam in the weaving machine and unwound therefrom. After interlacing weft thread, a fabric is formed which is drawn by the withdrawing beam. The tension on the warp threads should have an optimum constant value.
For the purpose of achieving this condition, a regulator is needed. In weaving machines such a sensor generally takes the form of a cylinder which bears against the threads being unwound from the warp beam. Let-off motions of the unwinding warp threads for detecting variations of tension by the sensor are used, i.e., a cylinder or roller on a resilient swingable lever. A variable speed gear box is operatively connected to the cylinder and is the main member of such a regulator. The variable speed gear box is generally controlled via a transmission member with the cylinder or roller. The output shaft of the variable speed gear box drives the warp beam via a transmission mechanism. In this type of regulator, a direct dependence, that is, a proportional dependence, is encountered between the deviation of the back rest (i.e., the cylinder or roller) and the adjustment of the angular velocity of the output shaft of the regulator. Thus the regulator has strictly a proportional behavior which is disadvantageous. This deviation of the cylinder or roller increases due to the decrease of the warp threads winding radius on the warp beam in the course of weaving which causes a higher number of yarn breakages and consequently a lower quality of the fabric obtained.